Portion of a display screen with a graphical user interface



FIG. 1 is a front view of a portion of a display screen with a graphical user interface showing the new design; and,

FIG. 2 is a front view of a second embodiment thereof.

The dashed lines showing lines and images form no part of the claimed design. Said dashed lines and dashed image are presented only for environmental purposes. 

CLAIM The ornamental design for a portion of a display screen with a graphical user interface, as shown and described. 